Steve and Corey talk to Elizabeth Kolbert, author of the Sixth Extinction, about the current state of the climate debate. All three are pessimistic about the possibility that emissions will be substantively reduced in the near term, and they discuss technologies for removing carbon from the atmosphere. They explore uncertainty in the models regarding temperatures rise and precipitation, and contemplate a billion people are on the move in response to climate change and population increase. They ask: what is more of a threat to humanity in the coming century, runaway AI or runaway climate change?